181811881

This number is a prime.

Just showing those entries submitted by 'Petrov': (Click here to show all)

Emirp formed by the concatenation in order of all three-digit primes containing 1 and 8. If we replace the 8s (2^3) with 2, 3, 2*3 and 3^2 it will yield 4 more primes. The same also works with 2*3*6*8*9. Curiously 1818118810188118181 is prime too. [Petrov]